import javax.sound.midi.Soundbank;
import java.util.Scanner;

public class Main1598 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double x = sc.nextDouble();
        double y = sc.nextDouble();
        double n = sc.nextDouble();
        double z = n - (x + y) * 0.9;
        System.out.println(String.format("%.1f", z));
    }
}
